Nick

> Measuring the thickness of intermetallic layers is only possible with micro sections.
> Measuring the strength of solder joints is not easy in my opinion. There are tests like shearing the components. However, I am not convinced regarding the validity of the results. If you wish to do tests of this kind I suggest to pay attention to the following points:
- The shear strength of soft solder depends on the deformation speed applied. The faster the material is deformed the higher the shear strength. 
- The deformation behaviour ( Load- deformation rate relationship ) is temperature dependent.
- The point, where the shear force is applied is important regarding the state of stress in the solder joint ( shear stress / tensile stress ). 
Thus, in my opinion, these tests are in the best case relative measurements. This means that only results with the same measurement parameters can be compared.
Additionally I believe that the variations in the geometry of solder joints and of the measurement itself contribute at least to the same variation in the measurement results than voids unless your solder joints are rather a Swiss cheese or very poorly wetted.

In think, the best you can do is micro sections in regular intervals and keeping your process under control. If the solder joints are metallurgically OK there is no point to concern about their strength.

Best regards

Guenter

Guenter Grossmann
Swiss Federal Institute for Materials Testing and Research EMPA
Centre for Reliability
8600 Duebendorf
Switzerland

Phone: xx41 1 823 4279
Fax :      xx41 1823 4054
mail:     [log in to unmask]

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